Efficient difference-frequency mixing of diode lasers in lithium niobate channel waveguides

Abstract.

Reported are design, fabrication recipes, and performance of channel waveguides for mid-infrared difference-frequency mixing of diode lasers. The waveguides were formed by annealed proton exchange in periodically poled lithium niobate, and included a mode filter, a taper, and a mixing channel. Two designs of the mode filter and taper were investigated, one involving periodic segmentation. Device efficiencies of 1.4 % W^-1-4.0 % W^-1 were achieved for difference-frequency generation in the 2.8–3.6 μm wavelength region using near-infrared diode lasers as pump sources. Up to 136 μW output power was obtained at 2.8 μm with 198 mW total launched power. Measured conversion efficiencies were typically four times lower than predicted. Departure of the taper behavior from adiabatic contributed to this discrepancy.